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Why are so many cot mattresses failing safety tests?

We've found safety issues in more than 60% of cot mattresses we've tested recently. Find out what they are, and how you can ensure a secure night's sleep for your baby

Why are so many cot mattresses failing safety tests?

Which? has tested 18 cot mattresses from big brands over the past two years. We’ve named 12 of these cot mattresses Don’t Buys because they failed key safety tests that make up part of the 2017 British Safety Standard.

We’re concerned by this high failure rate and we want parents to be vigilant in terms of spotting these potential issues with their own cot mattresses.

Read on to find out what we discovered in our tests, and how you can ensure a suitable and safe sleeping environment for your little one.

Best Buy cot mattresses – read reviews of the impressive cot mattresses that passed our stringent tests.

Safety tests cot mattresses are failing

Our cot mattress safety tests replicate those in the current cot mattress safety standard, which is called BS EN 16890:2017.

It was approved in September 2017, and it’s a voluntary standard which means that it’s not a requirement; however manufacturers are strongly encouraged to meet these standards to minimise risks and hazards for babies and young children.

The four key safety tests we’ve seen cot mattresses repeatedly fail are:

Lack of firmness

A cot mattress is automatically downgraded to a 0% Don’t Buy if our tests highlight a serious safety risk.

If the top layers of the mattress are too soft and your baby accidentally rolls onto their front, their face could sink into the mattress. This poses a suffocation risk.

It’s a concern with babies aged between four and 12 weeks, when they are commonly able to roll over from their back to their front.

Rolling from front to back requires more strength, and in some cases a baby may not master this skill until they reach around six months old.

Both the Stokke Home Bed Mattress and Babydunlopillo Safer Sleep Cot Bed Mattress failed the firmness test when new, so for this reason we would recommend that you avoid these mattresses if your baby is less than six months old to mitigate this risk.

Stokke told us it has updated this mattress and the old product is no longer in circulation, but we haven’t verified this with our testing and the two products share the same name.

Baby Dunlopillo told us its mattress complies with all applicable mandatory safety standards. It did, however, remove the product from sale pending its own internal investigations.

Choking hazards

Ideally you want to invest in a cot mattress with a removable and washable cover to help keep your baby’s mattress clean. Many cot mattresses have a zip to help you remove the cover from the mattress easily.

But our tests identified cot mattresses with accessible zip pulls that can detach easily and become a choking risk or swallowing hazard.

This is an unnecessary risk which could be mitigated by having a small pocket for the zip pull, to ensure that little hands can’t reach it in the middle of the night.

Three out of the five cot mattresses we tested in December 2019 had zip pulls that came off in our tests, and one even had a sharp spike to lock the zip pull in place, which could cause injury.

If your child’s cot mattress has a zip pull that is easy to get to, we’d advise sticking a piece of strong tape, such as duct tape or gaffer tape, over the top and adding a tightly-fitted sheet onto the mattress to further restrict access to the zip pull.

Cover shrinkage

While cover shrinkage may not immediately seem something serious – with cot mattresses a shrunken cover can compress the mattress and shrink its size.

The smaller dimensions might mean that the mattress no longer sits flush within the cot bed and if there’s a gap of a few centimetres, there’s a risk a baby can trap a limb and become stuck.

If your baby becomes trapped and is positioned face down, then it could be a serious suffocation risk.

Six of the 18 mattresses we’ve tested in the past two years have had this issue. One shrunk from 139.5cm to 134.5cm, potentially creating a dangerous 5cm gap where a child can get caught between the mattress and the cot.

Incorrect dimensions

As we’ve mentioned, the size of your cot mattress is very important and there shouldn’t be any gaps between the mattress and the cot or bed that are more than 3cm. The mattress should also be firm and very flat.

Manufacturers should be making cot mattresses that are 140 x 70cm or 120 x 60cm, which are the standard sizes for cot and cot bed mattresses.

But there’s clearly a quality control issue, as some cot mattresses we’ve tested are either too small (potentially causing an unsafe gap) or too large which means they don’t sit flat.

We’ve also seen incorrect information and wrong advice on cot mattress labels and instructions that could compromise a baby’s safety.

Read our cot mattress safety guide to find more tips and advice about using your cot mattress safely.


Stickers may seem innocuous, but there are two reasons why manufacturers shouldn’t be putting them on cot mattresses.

Firstly a sticker is a potential suffocation hazard and a choking risk should your little one decide to play with it and put it in their mouth.

Secondly these stickers typically include important information, such as the suitable side for sleeping or the age restrictions for each side, which should be permanently attached to the mattress to help parents use the product safely.

For example, the Silver Cross Superior Cot Mattress (pictured below) is permanently labelled with a ‘baby side’ for little ones under 18 months old and a ‘toddler side’ for children of more than 18 months to guide parents when using it.

If you buy a cot mattress that has a sticker on it, make sure to remove it before use and note down the information either on the label, or somewhere safe so you can refer to it if need be.

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